Initiation of the breeding season in ewe lambs and goat kids with melatonin implants

Sixty-eight female and 4 male lambs of the Chios breed born in autumn (September–October) and 48 female and 4 male kids of the Damascus breed also born in autumn (November), were used to evaluate the effect of melatonin implants (Regulin®) on the initiation of the breeding season. For each species and sex, half of the animals were either left untreated to serve as controls (C) or received ear implants (females one and males two implants) of melatonin (MEL) in May (spring). Each C and MEL group of females was kept separately and away from males for 5 weeks after implantation and then, C and MEL males were joined with the respective groups for 45 (sheep) and 35 days (goats). Animals not conceiving during the early June–July breeding season, were mated again in September (natural breeding season). The reproductive performance and the 60-day milk yield of animals giving birth during the two seasons were compared. Early in the season (mid November–December), significantly more MEL than C ewes and goats gave birth (75.5% versus 23.5%, p < 0.01; 70.8% versus 37.5%, p < 0.05, respectively). For both species, most of the other characteristics examined were significantly affected by season, but not by treatment. Females giving birth early in the season were approximately 80 days younger at parturition and recorded a lower body weight at mating than those giving birth in the natural February–March season. In the first mating period, the animals mated and conceived had similar body weights to those not mated. The natural, compared with the early June–July mating season, was associated in sheep with higher litter weight at birth (7.0 kg versus 5.8 kg, p < 0.05) and in sheep and goats with a higher number (p < 0.05) of offspring born live (1.78 versus 1.38; 2.0 versus 1.61, respectively) and weaned (1.74 versus 1.36; 1.82 versus 1.35, respectively). Total litter size at birth and 60-day milk yield after weaning, were not significantly different between the two seasons. It could be concluded that melatonin implants administered during the last month of spring in autumn-born female Chios sheep and Damascus goats, advanced the initiation of their breeding season by about 80 days when joined with young males also treated with melatonin implants. The overall reproductive performance and milk yield of animals breeding early, was satisfactory and comparable to that of animals breeding in the natural breeding season

Seasonal effects on puberty and reproductive characteristics of female Chios sheep and Damascus goats born in autumn or in February

Ten Chios ewe lambs and 10 Damascus she-kids born in October–November and similar numbers born in February along with eight multiparous females from each species, were used to examine pubertal events and reproductive seasonality. Reproductive activity was monitored by determining serum progesterone concentrations once a week for 12 months. The mean date of onset of ovulation (puberty) in autumn-born Chios females (7 August) was earlier (p<0.05) than in February-born ones (11 September) though the onset of regular cyclicity was not significantly different between the two groups (30 August and 19 September, respectively). The age and live weight at puberty in autumn-born females was higher (p<0.01) than in February-born ones, the respective values being 43.3 weeks and 50.1 kg, versus 29.9 weeks and 42.0 kg. All animals, irrespective of time of birth, started ovulating after the summer equinox. Multiparous Chios ewes had reproductive cycles covering most time of the year with acyclic periods during spring and summer. In ewe lambs, about half of the animals ceased cycling during the second half of winter and in spring, while the rest continued cycling. The total number of cycles detected over the experimental period was lower (p<0.05) for February-born (n=9.4) compared with autumn-born females (n=13.7) and adult ewes (n=17.1). In Damascus she-kids born in autumn or in February, onset of puberty was at the same time in the following autumn, the respective mean date for the two groups being 1 November and 27 October. For autumn-born animals, age (48.4 weeks) and live weight (53.8 kg) at puberty were higher (p<0.01) than for those born in February (37.3 weeks, 42.9 kg). Reproductive cycles in adult goats started in the second half of September and continued until the end of March. Most young goats (75%) had their last seasonal cycle in February and the rest in March. The total number of cycles was higher (p<0.01) in adult (n=8.1) than in young goats born either in autumn (n=6.3) or in February (n=5.7). It is concluded that reproductive development and puberty in Chios female sheep are mostly under seasonal influences though age and body weight are also contributing factors. This breed has a long reproductive season with some animals cycling throughout the year. The Damascus female goat is strictly seasonal with distinct periods of reproductive cyclicity and inactivity. Puberty attainment of Damascus females born in autumn or in February is at the same time the following autumn

Identification of established genetic variants associated with milk traits

The present study investigated the genetic diversity of small ruminant breeds of Cyprus, regarding β-lactoglobulin (β-LG) genotypes and the existence of bovine single nucleotide polymorphisms (SNPs). In total, 366 animals belonging to the Chios and Cyprus fat-tailed sheep breeds, and to the Damascus and Machaeras goat breeds, were genotyped for the identification of the most common β-lactoglobulin variants (A and B), as well as for the presence of the growth hormone receptor (GHR) F279Y and the acylCoA:diacylglycerol acyltransferase 1 (DGAT1) K232A SNPs. With regard to β-lactoglobulin genotypes, two genetic variants (A and B) were identified for the sheep breeds and only one variant (A) for the goat breeds. The results showed that variant B of β-LG gene was not present in any caprine sample and therefore a fixed A-allelic genotype was suggested for both goat breeds. However, the present study showed that the Cyprus fat-tailed sheep was predominantly of the β-LG B type demonstrating significant differences in allelic frequencies (P < 0.001) and genotypic distributions (P < 0.05) compared to Chios sheep, revealing unusually high distribution of the BB genotype (38.5% of the total genotypes) as compared to Chios (4.5%) or other Mediterranean sheep breeds. With regard to bovine SNPs, the present study investigated the existence of GHR F279Y and the DGAT1 K232A SNPs, which have both been previously well documented in cattle as having strong effects on milk yield and composition. Although we were able to confirm the presence of both of these mutations in bovine sample controls by both allele specific PCR reactions and direct DNA sequencing, we were unable to detect them in all four major pure breeds of sheep and goats supporting the small ruminant dairy industry in Cyprus

Nutritional effects on puberty and production performance of ewe lambs and goat kids

Chios ewe lambs and Damascus goat kids born in autumn or spring were used to study nutritional effects during development on their performance. Within species and season of birth, the animals were allocated at random to 3 equal sized groups. Group A animals were put on a high, group B on a medium plane of nutrition and group C on a medium plus increased protein intake from 3 weeks prior to the start and until the end of mating. At monthly intervals, the animals were weighed and feed offered was adjusted accordingly. Following mating, all animals were housed and fed as a single group at slightly above maintenance plus a pregnancy allowance for the last 6 weeks prepartum. With the exception of the induced higher BW at mating, daily BW gain and daily concentrate and roughage intake until mating of animals in group A compared to those in B and C, there were no differences among treatments for litter size and 60 d milk yield in either autumn born or spring born lambs and kids. Similarly, there was no difference among treatments in the no. of animals pregnant and delivering. Based on the findings of the present study it may be concluded that there is no need for BW greater than 44 kg (around 65% of mature BW) at mating and of additional (>14% CP DM) protein 3 weeks prior to start and until the end of mating to attain higher productive and reproductive performance of lambs and kids

Evidence of major gene(s) affecting milk traits in the Chios sheep breed

This study investigates the mode of inheritance and estimates the genetic parameters of milk yield, milk fat content, and litter weight at birth in Chios sheep breed. A complex pedigree and repeated records for milk and fat content as well as litter weight from two distinct and unrelated populations, spanning over 20 and 31 years, were used for the detection of a major gene for milk yield in the Chios breed. The data originated from a closed nucleus in Northern Greece (6021 repeated records) and from a closed nucleus in Cyprus (6965 repeated records). The genetic parameters were estimated using both a polygenic model with maximum likelihood methodology and a mixed inheritance model (polygenes + major gene), using Bayesian segregation analysis. Segregation analysis results support the presence of a major gene for milk yield segregating in both populations. The mixed inheritance model for milk yield appears to be the most suitable model. The estimated additive effect of the putative major gene was 11% and 10.5% of the total additive genetic variance in the Cypriot and Greek populations, respectively, while the estimated dominance effect was negative in both populations. Although there are some indications for a major gene affecting fat content in Chios breed, there is no evidence for the presence of a major gene affecting litter weight at birth in either populatio

Genetic analysis of Chios sheep: Identification of genetic variants and investigation of their association with milk traits.

Dissecting the genetic basis of milk production traits would be of great benefit to the small ruminant dairy industry. The objective of this work was to identify genetic variants at loci that have been mainly mapped in dairy cattle, and investigate their effects on milk traits of Cyprus Chios sheep. For this purpose, 320 Chios ewes from a nucleus flock in Cyprus were genotyped for polymorphisms at the β-lactoglobulin (β-LG), prolactin (PRL), Growth Hormone Receptor (GHR), DGAT1, and Acetyl-Coenzyme A acyltransferase-2 (ACAA2) loci. The GHR F279Y and DGAT1 K232A variants were absent from Chios sheep. The common β-LG variants, A and B, and PRL variants were detected at intermediate frequencies but exhibited no association with milk traits. The entire coding region of ACAA2 was sequenced and a novel SNP (HM537015:g.2982T > C) was identified in the 3’ UTR, with both alleles segregating at similar frequencies. All other exons were monomorphic. Mixed model association analysis, using SNP data from 318 animals from 104 paternal half-sib families and first lactation phenotype and pedigree information on 2405 ewes revealed that this SNP was significantly associated with milk yield. The T allele was associated with increased milk yield, and exhibited partial dominant action. Animals with the g.2982TT or g.2982CT genotype had significantly higher milk yield than those with the g.2982CC genotype, with the g.2982T allele having an additive effect of 13.4(±4.7) kg and a dominance effect of 7.9(±6.1) kg. Based on estimated allelic effects and sample allele frequencies, the g.2982T>C SNP explained 10% of the additive genetic variance for milk yield. To the best of our knowledge, this is the first study reporting a significant association of an ACAA2 polymorphism with milk yield in ruminants. Whether this (or a closely linked) SNP is a quantitative trait nucleotide for milk yield remains to be determined